In a pusher axle suspension system of a vehicle, a rear wheel shaft of a large vehicle e.g., a vehicle having five shafts, moves up when the vehicle is unloaded and moves down when the vehicle is loaded. That is, when the vehicle is empty, travel resistance decreases by moving up a pusher axle when pusher axle tends to move down. When the vehicle is loaded, an accumulated load is supported by moving the pusher axle downwards.
The pusher axle suspension system includes a lift air spring to move the pusher axle up/down according to an electric signal of an up/down switch, and a ride air spring to absorb vibration from a road surface when the pusher axle moves down by the lift air spring.
FIG. 1 is a perspective view illustrating a pusher axle suspension system applied to an existing pusher axle vehicle.
Referring to FIG. 1, a pusher axle suspension system includes a front frame 101, an axle sheet 103, a pusher axle 105, a lift arm 107, a lift air spring 109, and a ride air spring 111.
The front frame 101 is mounted on a vehicle body, a front end of the axle sheet 103 is coupled with the front frame 101 through a mounting bush, and a rear end of the axle sheet 103 is supported at the pusher axle 105 having a wheel which is axially coupled. A front end of the lift arm 107 is coupled with the front frame 101 through the mounting bush, and a rear end of the lift arm 107 is coupled to the axle sheet 103 by a hinge.
The lift air spring 109 is disposed between the axle sheet 103 and the lift arm 107 so that the axle sheet 103 and the lift arm 107 perform a three bar link operation through air pressure supply control to control up/down operations of the pusher axle 105.
In addition, the ride air spring 111 is installed between the pusher axle 105 and the vehicle body to absorb vibration from a road surface.
Here, the lift air spring 109 and the ride air spring 111 are connected to an air tank (not shown) through an air pressure supply hose (not shown), and control air pressure through a solenoid valve (not shown).
Accordingly, the lift air spring 109 controls the up/down operations of the pusher axle 105 through the air pressure supply control, and the ride air spring 111 absorbs vibration from the road surface as the pusher axle 105 moves down.
However, the existing pusher axle suspension system requires the lift air spring 109 and the ride air spring 111 so that a configuration is complicated together with an air supply system, and productivity is deteriorated.
In addition, upon the up/down operations of the axle sheet 103 by the lift air spring 109, a load is concentrated on the mounting bush to connect the axle sheet 103 and the lift arm 107 with the front frame 101 so that lifespan of the mounting bush is reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.